Human metapneumovirus (HMPV) is a virus that was first recovered in the Netherlands from infants and children experiencing acute respiratory tract disease (van den Hoogen et al. Nat. Med. 7:719-724, 2001; De Jong et al. WO 02/057/302 A2).
HMPV is worldwide in prevalence and resembles human respiratory syncytial virus (RSV or HRSV) with regard to disease signs and the ability to infect and cause disease in the young infant as well as individuals of all ages (for a review, see Heikkinen and Jarvinen, Lancet 361:51-59, 2003).
HMPV is characterized as an enveloped virus with a genome that is a single negative strand of RNA of approximately 13 kb. The virus has been classified presumptively in the Metapneumovirus genus, Pneumovirus subfamily, Paramyxovirus family of the Order Mononegavirales, comprising the nonsegmented negative strand RNA viruses or mononegaviruses. Mononegaviruses also are called nonsegmented negative strand RNA viruses. The Paramyxovirus family has two subfamilies, Paramyxovirinae and Pneumovirinae (also referred to as paramyxoviruses and pneumoviruses, respectively).
Several other mononegaviruses are important agents of respiratory tract disease in pediatric and other populations, for example, RSV and human parainfluenza virus types 1, 2 and 3 (HPIV1, HPIV2 and HPIV3). Although these viruses have some similarities with HMPV, their sequences are different from the HMPV viruses disclosed herein.
Since HMPV was described only recently, there is little documented experience with its propagation, manipulation and stability, and there are no well established or widely available reference strains, mutant strains, reported vaccine candidates, or reference virus-specific antibodies or comparable reagents or systems or experimental animals models to facilitate characterization. Because HMPV is associated with severe respiratory tract disease, there is a need to develop methods to engineer sale and effective vaccines to alleviate the serious health problems attributable to this pathogen, particularly among young infants.